Nashville Interstate AC Service's technician, Lance Waterbarger, reveals three secrets as he completes a fall maintenance check on an 11-year-old York HVAC dual-fuel furnace in the basement of a customer's home. The unit is high efficiency and uses a heat pump and a gas furnace. This video describes the maintenance checks Lance does on the burners for the gas furnace.

1. Check the burners

Remove the cover from the metal housing around the burners. There is a hot surface igniter on the left side and a flame sensor on the right side. Fuel is ignited on the left and the flame will roll down the line towards the right. If the flame sensor doesn’t sense a flame on the last burner, the burner will shut off and try again. The flame sensor is one part of the safety equipment on a gas furnace. Lance checks all the safeties.

2. Check the inducer motor and associated switches

Check the inducer motor and associated switches. The inducer motor gets the air moving throughout the system, causing a "draft" (positive pressure), so that the combustion gases will travel up the flue. If the inducer motor does not come on, the furnance will shut down as a safety mechanism. There is a vacuum hose connected to a pressure switch or fan proofing switch to ensure that there is a draft for the flue. The pressure switch sends a signal through two wires and tells the circuit board to initiate the heat sequence. Check that the hose is not clogged up, and that the switch is closing. Make sure the switch is sending a signal back to the main circuit board.

3. Check the air supply and flue

Be sure the air input pipe is not capped off or plugged up. It needs to be pulling fresh air into the combustion chamber. Check that the flue is exhausted to the outside. If there are any breaks in either of these, or if they are plugged up, this would be a serious safety concern.